The present invention relates to a disc drive microactuator, and more particularly to a high resolution positioning mechanism for selectively moving a transducer portion of the slider radially with respect to circumferential data tracks of a rotatable disc.
The density of concentric data tracks on magnetic discs continues to increase (that is, the size of data tracks and radial spacing between data tracks are decreasing), thereby requiring more precise radial positioning of the head. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuator motor, such as a voice coil motor, to position a head on a flexure at the end of the actuator arm. The large-scale motor lacks sufficient resolution and bandwidth to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism is necessary to accommodate the more densely spaced tracks. Another challenge is that the track density of magnetic discs increases as the flying height of the transducer head above the surface of the disc must decrease for effective data writing and reading, without compromising the reliability of the head-to-disc interface due to wear. As the fly-height becomes lower, it becomes more critical to maintain the fly-height precisely at a desired value. A slight decrease may cause contact between the head and the disc, which could cause a catastrophic failure, and a slight increase during writing or reading could cause errors in transducing data with the disc.
One promising approach for high resolution head positioning involves employing a high resolution microactuator in addition to the conventional low resolution actuator motor, thereby effecting head positioning through dual-stage actuation. Various microactuator designs have been considered to accomplish high resolution head positioning. Various locations for the microactuator have been suggested, including, for example, on the slider, on the gimbal, at the interface between the gimbal and the slider, and on the actuator arm. However, the previous designs have had shortcomings that limited the effectiveness of the microactuator, such as substantial performance limitations or manufacturing complexities, which made the microactuator designs impractical. An effective microactuator design must provide high acceleration in positioning the head while also generating sufficiently large and accurate displacements to precisely move the head across several data tracks on the disc.
Transducer-level microactuators allow precise off-track positioning for high-TPI data storage and active fly-height control. Typically, transducer-level microactuators include a main slider body and a movable rotor containing the transducer. The rotor is connected to the slider body by spring flexures. An actuation method, such as electrostatic electrodes or electromagnetic coils, is used to provide offtrack and/or fly-height actuation (or rotor preload forces). Previously disclosed fabrication methods for transducer-level microactuators depend heavily on deep reactive ion etched (DRIE) and high aspect ratio spring flexures between the rotor and the slider body. In general, the slider body is comprised of silicon and the spring flexures are etched out of the slider body to form the high aspect ratio silicon spring flexures. However, use of a silicon substrate is not ideal because it is not a standard material, is less understood and is not as robust than the standard alumina titanium carbide (Al2O3TiC) slider. In addition, silicon slider bodies have an increased likelihood of chipping, cracking, breakage, and/or other damage when the slider body is in use or if the hard drive is dropped. There is a need in the art for a transducer-level microactuator that can be made from standard Al2O3TiC or other carbon based substrate material, is more robust, less likely to break during use, and easy to fabricate.